I recently purchased an 89' Ford F-150 XLT Lariat V-6 4.9 300. I drove the truck a few times and it ran great. However, I noticed the radiator had a small leak. Anyway, drove to a local auto parts store to pick up some radiator leak sealent. When I drove away a new issue arose. I hadn't done anything yet with the sealent. The engine was sputtering out. I was able to keep it running by feathering the gas pedal. I was able to get it home. The same thing happened repeatedly. It starts perfectly, but then after a minute or two it begins to sputter out...like it's not getting gas or something. I'm able to keep it started by feathering the gas pedal until I get the RPMs up high for an extended period. Then it will run fine for a minute.

At first I thought it was the fuel filter. So I replaced it but same issue. I then purchased a code reader. It told me two codes, 23 and 34.

Ok at the back of the engine on the left hand side next to the valve cover there is the fuel rail and the last injector there is a fuel pressure port it looks like a valve stem for a tire . You screw the fuel pressure gauge on the port. Then you just key on and off then get the reading of the gauge it should read around 45 psi and the when the key on and
Engine running it should be 50 to 55 psi. I have seen sum
Readings around 60 psi. I hope this helps.

Ok at the back of the engine on the left hand side next to the valve cover there is the fuel rail and the last injector there is a fuel pressure port it looks like a valve stem for a tire . You screw the fuel pressure gauge on the port. Then you just key on and off then get the reading of the gauge it should read around 45 psi and the when the key on and
Engine running it should be 50 to 55 psi. I have seen sum
Readings around 60 psi. I hope this helps.

Thank you so much for tell me where I could find that valve. I could not find it.

Anyway good news...I think. I checked my Haynes book and it said the psi for the truck should be between 35 and 40. Mine idled at 39 psi for about a minute or so. Then it dropped, slowly and when it did the engine began to run rough...like it was sputtering out. The problem. It dropped from 39 all the way below 20...maybe close to 10. I was able to keep it running by throttling it in waves to get the engine back up. When I was doing this, the pressure seemed to stay around 20 psi. Once the engine was running high enough RPMs for about 30 seconds I backed off the throttle. The pressure went back up to 39 psi. The process repeated itself again before I came back inside to report.

Hook the fuel pressure gauge back up to the truck and with the engine running pull off the vacum line that runs to the fuel pressure regular if the gauge reads high its the regulator if its low its the pump. Also when you pull of the vacum line going to the fuel pressure regular look to see if its wet with gas thats another sign of a bad fuel pressure regular.

Thank you so much for tell me where I could find that valve. I could not find it.

Anyway good news...I think. I checked my Haynes book and it said the psi for the truck should be between 35 and 40. Mine idled at 39 psi for about a minute or so. Then it dropped, slowly and when it did the engine began to run rough...like it was sputtering out. The problem. It dropped from 39 all the way below 20...maybe close to 10. I was able to keep it running by throttling it in waves to get the engine back up. When I was doing this, the pressure seemed to stay around 20 psi. Once the engine was running high enough RPMs for about 30 seconds I backed off the throttle. The pressure went back up to 39 psi. The process repeated itself again before I came back inside to report.

So what does all this mean?

Thanks,
Don

Well my 87 fuel pressure does not run that low mine runs
On the high side. Cool hope this helps good luck.